Current platelet storage conditions, which utilize platelet-rich plasma at room temperature, are associated with a progressive platelet activation and are a good media for bacterial growth if contamination occur during collection. An ideal synthetic storage media is one that would prevent bacterial growth and extend the platelet storage period beyond five days. In the search for this media, it is necessary to evaluate platelets stored in the new medium against conventionally stored platelets. We have found that the selection of appropriate resuspension media after storage significantly affects the performance of the platelets in in vitro tests. The resuspension medium must be the same for both test and control platelets so that a fair comparison of platelets stored under novel conditions may be performed. The risk of bacterial contamination could be reduced if platelets were stored in cold temperatures but cold exposure has a negative impact on the survival of platelets in circulation after transfusion. Moreover, such conditions potentiate the responsiveness of platelets to certain agonists in platelet aggregation although it is not clear whether this contributes to the shortened circulation times. We are investigating the mechanisms involved in the potentiation of aggregation responses. Cold temperatures exposure does not increase agonist-induced fibrinogen binding or increase the number of fibrinogen binding sites. However, aggregates of cold exposed platelets are more resistantnt to disaggregating agents suggesting that this resistance may be the mechanism for the potentiated aggregation resistance.